in_array()

(PHP 4, PHP 5, PHP 7)

检查数组中是否存在某个值

说明

in_array(mixed $needle,array $haystack[,bool $strict=FALSE]): bool

大海捞针，在大海（$haystack）中搜索针（$needle），如果没有设置$strict则使用宽松的比较。

参数

$needle

待搜索的值。

Note:

如果$needle是字符串，则比较是区分大小写的。

$haystack

待搜索的数组。

$strict

如果第三个参数$strict的值为TRUE则in_array()函数还会检查$needle的类型是否和$haystack中的相同。

返回值

如果找到$needle则返回TRUE，否则返回FALSE。

范例

Example #1in_array()例子

<?php
$os = array("Mac", "NT", "Irix", "Linux");
if (in_array("Irix", $os)) {
    echo "Got Irix";
}
if (in_array("mac", $os)) {
    echo "Got mac";
}
?>

第二个条件失败，因为in_array()是区分大小写的，所以以上程序显示为：

Got Irix

Example #2in_array()严格类型检查例子

<?php
$a = array('1.10', 12.4, 1.13);
if (in_array('12.4', $a, true)) {
    echo "'12.4' found with strict check\n";
}
if (in_array(1.13, $a, true)) {
    echo "1.13 found with strict check\n";
}
?>

以上例程会输出：

1.13 found with strict check

Example #3in_array()中用数组作为 needle

<?php
$a = array(array('p', 'h'), array('p', 'r'), 'o');
if (in_array(array('p', 'h'), $a)) {
    echo "'ph' was found\n";
}
if (in_array(array('f', 'i'), $a)) {
    echo "'fi' was found\n";
}
if (in_array('o', $a)) {
    echo "'o' was found\n";
}
?>

以上例程会输出：

  'ph' was found
  'o' was found

参见

• array_search() 在数组中搜索给定的值，如果成功则返回首个相应的键名
• isset() 检测变量是否已设置并且非 NULL
• array_key_exists() 检查数组里是否有指定的键名或索引

Loose checking returns some crazy, counter-intuitive results when used with certain arrays. It is completely correct behaviour, due to PHP's leniency on variable types, but in "real-life" is almost useless.
The solution is to use the strict checking option.
<?php
// Example array
$array = array(
  'egg' => true,
  'cheese' => false,
  'hair' => 765,
  'goblins' => null,
  'ogres' => 'no ogres allowed in this array'
);
// Loose checking -- return values are in comments
// First three make sense, last four do not
in_array(null, $array); // true
in_array(false, $array); // true
in_array(765, $array); // true
in_array(763, $array); // true
in_array('egg', $array); // true
in_array('hhh', $array); // true
in_array(array(), $array); // true
// Strict checking
in_array(null, $array, true); // true
in_array(false, $array, true); // true
in_array(765, $array, true); // true
in_array(763, $array, true); // false
in_array('egg', $array, true); // false
in_array('hhh', $array, true); // false
in_array(array(), $array, true); // false
?>

<?php
class Method {
  /** @var int current number of inMultiArray() loop */
  private static $currentMultiArrayExec = 0;
  /**
   * Checks if an element is found in an array or one of its subarray.
   * The verification layer of this method is limited to the parameter boundary xdebug.max_nesting_level of your php.ini.
   * @param mixed $element
   * @param array $array
   * @param bool $strict
   * @return bool
   */
  public static function inMultiArray($element, array $array, bool $strict = true) : bool {
    self::$currentMultiArrayExec++;
    if(self::$currentMultiArrayExec >= ini_get("xdebug.max_nesting_level")) return false;
    foreach($array as $key => $value){
      $bool = $strict ? $element === $key : $element == $key;
      if($bool) return true;
      if(is_array($value)){
        $bool = self::inMultiArray($element, $value, $strict);
      } else {
        $bool = $strict ? $element === $value : $element == $value;
      }
      if($bool) return true;
    }
    self::$currentMultiArrayExec = 0;
    return isset($bool) ? $bool : false;
  }
}
$array = array("foo" => array("foo2", "bar"));
$search = "foo";
if(Method::inMultiArray($search, $array, false)){
  echo $search . " it is found in the array or one of its sub array.";
} else {
  echo $search . " was not found.";
}
# foo it is found in the array or one of its sub array.

If you're working with very large 2 dimensional arrays (eg 20,000+ elements) it's much faster to do this...
<?php
$needle = 'test for this';
$flipped_haystack = array_flip($haystack);
if ( isset($flipped_haystack[$needle]) )
{
 print "Yes it's there!";
}
?>
I had a script that went from 30+ seconds down to 2 seconds (when hunting through a 50,000 element array 50,000 times).
Remember to only flip it once at the beginning of your code though!

in_array() may also return NULL if the second argument is NULL and strict types are off.
<?php
var_dump(in_array(1, null));
?>
The output is NULL
If the strict mode is on, then this code would end up with the TypeError

For a case-insensitive in_array(), you can use array_map() to avoid a foreach statement, e.g.:
<?php
  function in_arrayi($needle, $haystack) {
    return in_array(strtolower($needle), array_map('strtolower', $haystack));
  }
?>

Determine whether an object field matches needle.
Usage Example:
---------------
<?php
$arr = array( new stdClass(), new stdClass() );
$arr[0]->colour = 'red';
$arr[1]->colour = 'green';
$arr[1]->state = 'enabled';
if (in_array_field('red', 'colour', $arr))
  echo 'Item exists with colour red.';
if (in_array_field('magenta', 'colour', $arr))
  echo 'Item exists with colour magenta.';
if (in_array_field('enabled', 'state', $arr))
  echo 'Item exists with enabled state.';
?>
Output:
--------
Item exists with colour red.
Item exists with enabled state.
<?php
function in_array_field($needle, $needle_field, $haystack, $strict = false) {
  if ($strict) {
    foreach ($haystack as $item)
      if (isset($item->$needle_field) && $item->$needle_field === $needle)
        return true;
  }
  else {
    foreach ($haystack as $item)
      if (isset($item->$needle_field) && $item->$needle_field == $needle)
        return true;
  }
  return false;
}
?>

This code will search for a value in a multidimensional array with strings or numbers on keys.
function in_multiarray($elem, $array)
{
  while (current($array) !== false) {
    if (current($array) == $elem) {
      return true;
    } elseif (is_array(current($array))) {
      if (in_multiarray($elem, current($array))) {
        return true;
      }
    }
    next($array);
  }
  return false;
}

If you found yourself in need of a multidimensional array in_array like function you can use the one below. Works in a fair amount of time
<?php
  function in_multiarray($elem, $array)
  {
    $top = sizeof($array) - 1;
    $bottom = 0;
    while($bottom <= $top)
    {
      if($array[$bottom] == $elem)
        return true;
      else 
        if(is_array($array[$bottom]))
          if(in_multiarray($elem, ($array[$bottom])))
            return true;
          
      $bottom++;
    }    
    return false;
  }
?>

In a high-voted example, an array is given that contains, amongst other things, true, false and null, against which various variables are tested using in_array and loose checking.
It impossible to receive false as a return value from in_array using loose checking if your arrays contains both the constants true and false. You might understandably trip over this (or the inverse - passing boolean true to check against an array of e.g. non-empty strings), but it's certainly not counter intuitive and makes perfect sense.

If you have an array like:
$arr = array(0,1,2,3,4,5);
in_array(NULL, $arr) returns true because you have 0 in your array. That is, in_array does not use === for equal check.

Since sometimes in_array returns strange results - see notes above.
I was able to find value in array by this quite a simple function;
<?php
/**
* $find <mixed> value to find
* $array<array> array to search in
*/
function _value_in_array($array, $find){
 $exists = FALSE;
 if(!is_array($array)){
  return;
}
foreach ($array as $key => $value) {
 if($find == $value){
    $exists = TRUE;
 }
}
 return $exists;
}
// Note
// You can't use wildcards and it does not check variable type
?>

I would like to add something to beingmrkenny at gmail dot com comparison post. After debugging a system, i discovered a security issue in our system and his post helped me find the problem.
In my additional testing i found out that not matter what you search for in an array, except for 0 and null, you get true as the result if the array contains true as the value.
Examples as php code :
<?php
$a = ['a', 32, true, 'x' => y];
var_dump(in_array(25, $a)); // true, one would expect false
var_dump(in_array('ggg', $a)); // true, one would expect false
var_dump(in_array(0, $a)); // false
var_dump(in_array(null, $a)); // false
?> 
Such the best practice in our case is to use strict mode. Which was not so obvious.

Recursive in array using SPL
<?php
function in_array_recursive($needle, $haystack) {
  $it = new RecursiveIteratorIterator(new RecursiveArrayIterator($haystack));
  foreach($it AS $element) {
    if($element == $needle) {
      return true;
    }
  }
  return false;
}
?>

Beware when using this function to validate user input:
$a = array('0' => 'Opt 1', '1' => 'Opt 2', '2' => 'Opt 3');
$v = 'sql injection';
var_dump(in_array($v, array_keys($a)));
This will result : true;
array_keys($a) will cast array keys to int instead of string !
then when in_array will compare it will cast 'sql injection' to int 0 !
Beware of this!

I found out that in_array will *not* find an associative array within a haystack of associative arrays in strict mode if the keys were not generated in the *same order*:
<?php
$needle = array(
  'fruit'=>'banana', 'vegetable'=>'carrot'
  );
$haystack = array(
  array('vegetable'=>'carrot', 'fruit'=>'banana'),
  array('fruit'=>'apple', 'vegetable'=>'celery')
  );
echo in_array($needle, $haystack, true) ? 'true' : 'false';
// Output is 'false'
echo in_array($needle, $haystack) ? 'true' : 'false';
// Output is 'true'
?>
I had wrongly assumed the order of the items in an associative array were irrelevant, regardless of whether 'strict' is TRUE or FALSE: The order is irrelevant *only* if not in strict mode.

If you're creating an array yourself and then using in_array to search it, consider setting the keys of the array and using isset instead since it's much faster.
<?php
$slow = array('apple', 'banana', 'orange');
if (in_array('banana', $slow))
  print('Found it!');
$fast = array('apple' => 'apple', 'banana' => 'banana', 'orange' => 'orange');
if (isset($fast['banana']))
  print('Found it!');
?>

In PHP array function the in_array() function mainly used to check the item are available or not in array.
In_array() Syntax:
in_array( 'search_item' , $array, boolean)
Where,
   boolean - It is used to check strict validation. And this field is optional one. If you want the strict validation you can use this.
We using in_array() function to performing following following two function. That is ,
1. Non-strict validation
2. Strict validation
1. Non-strict validation:
   This method to validate array with some negotiation. And it allow two parameters.
   For example,
     $array_sample = array ( 'key1' => 567 , 'key2' => 579);
     in_array('key1', $array_sample);  // output1: true
     in_array('577', $array_sample, false);  // output2: true
   Note: the Example 1, we use only two parameter. Because we can't mention `false` value. Because In default the in_array() take `false` as a boolean value.
   In above example, 
       Example 1 : The `key1` is not value in the array.  This is key of the array. So this scenario the in_array accept the search key as a value of the array.
       Example 2: The value `577` is not in the value and key of the array. It is some similar to the value `579`. So this is also accepted.
   So this reason this type is called non-strict function.
2. Strict validation
   This method to validate array without any negotiation. And it have three parameters. If you only mention two parameter the `in_array()` function take as a non-strict validation.
   For example,
     $array_sample = array ( 'key1' => 567 , 'key2' => 579);
     in_array('key1', $array_sample , true);  // output1: false
     in_array('577', $array_sample, true);  // output2: false
    
  This is return `true` only the search string is match exactly with the array value with case sensitivity.
Thanks for your time.

Watch out for this:
<?
print_r( (int) in_array('hello',array( 0 => 0)) );
?>
returns 1
Yes, it seems that is_array thinks that a random string and 0 are the same thing.
Excuse me, that's not loose checking, that's drunken logic.
Or maybe I found a bug?

If third parameter is not set to Strict then, the needle is found in haystack eventhought the values are not same. the limit behind the decimal seems to be 6 after which, the haystack and needle match no matter what is behind the 6th.
Wrong Response.
$os = array("652875063.10089021");
if (in_array("652875063.10089021", $os)) {
  echo "In Array";
}
Correct Response
$os = array("652875063.1008902");
if (in_array("652875063.1008901", $os)) {
  echo "In Array";
}

Esta función falla con las letras acentuadas y con las eñes. Por tanto, no sirve para los caracteres UTF-8. 
El siguiente código falla para na cadena = "María Mañas", no reconoce ni la "í" ni la "ñ":
  function validarNombreYApellidos ($cadena, $selector)
  {
    /* Se admiten las letras (he puesto sólo las mayusculas,
       porque paso la cadena con el nombre o
       el apellido a mayúscula antes de hacer la comparación), 
       las vocales acentuadas, la diéresis,
       las eñes, los espacios en blanco y el guión 
      (para los apellidos compuestos)*/
    $caracteresPermitidos = 
        array ("A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
             "N", "Ñ", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", 
             "Y", "Z", " ", "Á", "É", "Í", "Ó", "Ú", "Ü", "-");
    
    $correcto = true;
    // ¿La cadena está vacía?
    if (empty ($cadena))
    {
      $correcto = false;
    }
    else
    {
      $nombreOapellido = mb_strtoupper ($cadena, "utf-8");
      $longitudCadena = mb_strlen ($cadena, "utf-8");
      for ($i = 0; ($i < $longitudCadena) && $correcto; $i++)
      {
        if (!in_array ($nombreOapellido [$i], 
                   $caracteresPermitidos))
        {
          // Se ha encontrado un carácter no permitido
          $correcto = false;
        }
      }
    }
      return $correcto;
   }

Esta función falla con las letras acentuadas y con las eñes. Por tanto, no sirve para los caracteres UTF-8. 
El siguiente código falla para na cadena = "María Mañas", no reconoce ni la "í" ni la "ñ":
  function validarNombreYApellidos ($cadena, $selector)
  {
    /* Se admiten las letras (he puesto sólo las mayusculas,
       porque paso la cadena con el nombre o
       el apellido a mayúscula antes de hacer la comparación), 
       las vocales acentuadas, la diéresis,
       las eñes, los espacios en blanco y el guión 
      (para los apellidos compuestos)*/
    $caracteresPermitidos = 
        array ("A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
             "N", "Ñ", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", 
             "Y", "Z", " ", "Á", "É", "Í", "Ó", "Ú", "Ü", "-");
    
    $correcto = true;
    // ¿La cadena está vacía?
    if (empty ($cadena))
    {
      $correcto = false;
    }
    else
    {
      $nombreOapellido = mb_strtoupper ($cadena, "utf-8");
      $longitudCadena = mb_strlen ($cadena, "utf-8");
      for ($i = 0; ($i < $longitudCadena) && $correcto; $i++)
      {
        if (!in_array ($nombreOapellido [$i], 
                   $caracteresPermitidos))
        {
          // Se ha encontrado un carácter no permitido
          $correcto = false;
        }
      }
    }
      return $correcto;
   }

I just struggled for a while with this, although it may be obvious to others.
If you have an array with mixed type content such as:
<?php
 $ary = array (
  1,
  "John",
  0,
  "Foo",
  "Bar"
 );
?>
be sure to use the strict checking when searching for a string in the array, or it will match on the 0 int in that array and give a true for all values of needle that are strings strings.
<?php
var_dump( in_array( 2, $ary ) );
// outputs FALSE
var_dump( in_array( 'Not in there', $ary ) );
// outputs TRUE
var_dump( in_array( 'Not in there', $ary, TRUE ) );
// outputs FALSE
?>

hope this function may be useful to you, it checks an array recursively (if an array has sub-array-levels) and also the keys, if wanted:
<?php
function rec_in_array($needle, $haystack, $alsokeys=false)
  {
    if(!is_array($haystack)) return false;
    if(in_array($needle, $haystack) || ($alsokeys && in_array($needle, array_keys($haystack)) )) return true;
    else {
      foreach($haystack AS $element) {
        $ret = rec_in_array($needle, $element, $alsokeys);
      }
    }
    
    return $ret;
  }
?>

Add an extra if() to adrian foeder's comment to make it work properly:
<?php
  ...
  if (!@$ret) {
    $ret = rec_in_array($needle, $element, $alsokeys);
  }
  ...
?>
So this will work, too:
<?php
  $array = array(
    array('a', 'b'),
    array('c', 'd')
  );
  var_dump(rec_in_array('a', $array));
?>

You can use my function inArray, to search:
- multidimensional arrays
- for substrings (case [in]sensitive)
- for sub-arrays
- get array of keys of found values
Look at github https://gist.github.com/msegu/80093a65316ded5b69558d5456f80ff9 (here is too long)

A first idea for a function that checks if a text is in a specific column of an array.
It does not use in_array function because it doesn't check via columns.
Its a test, could be much better. Do not use it without test.
<?php
function in_array_column($text, $column, $array)
{
  if (!empty($array) && is_array($array))
  {
    for ($i=0; $i < count($array); $i++)
    {
      if ($array[$i][$column]==$text || strcmp($array[$i][$column],$text)==0) return true;
    }
  }
  return false;
}
?>

When using numbers as needle, it gets tricky:
Note this behaviour (3rd statement):
in_array(0, array(42)) = FALSE
in_array(0, array('42')) = FALSE
in_array(0, array('Foo')) = TRUE
in_array('0', array('Foo')) = FALSE

If you search for numbers, in_array will convert any strings in your array to numbers, dropping any letters/characters, forcing a numbers-to-numbers comparison. So if you search for 1234, it will say that '1234abcd' is a match. Example:
<?php
$test_array = array('test', '1234abcd');
if (in_array(1234, $test_array)) {
  echo '1234 is a match!';
}
?>

If you have a multidimensional array filled only with Boolean values like me, you need to use 'strict', otherwise in_array() will return an unexpected result.
Example:
<?php
$error_arr = array('error_one' => FALSE, 'error_two' => FALSE, array('error_three' => FALSE, 'error_four' => FALSE));
if (in_array (TRUE, $error_arr)) { 
  echo 'An error occurred';
}
else {
  echo 'No error occurred';
}
?>
This will return 'An error occurred' although theres no TRUE value inside the array in any dimension. With 'strict' the function will return the correct result 'No error occurred'.
Hope this helps somebody, cause it took me some time to figure this out.

var_dump(in_array('invalid', array(0,10,20))); 
The above code gives true since the 'invalid' is getting converted to 0 and checked against the array(0,10,20)
but var_dump(in_array('invalid', array(10,20))); gives 'false' since 0 not there in the array

Be careful to use the strict parameter with truth comparisons of specific strings like "false":
<?php
$truthy = [true, 'true', 1, '1', 'y', 'Y', 'yes', 'YES'];
if (in_array('false', $truthy)) {
  echo "False is truthy.\n";
} else {
  echo "False is not truthy.\n";
}
if (in_array('false', $truthy, true)) {
  echo "False is truthy.\n";
} else {
  echo "False is not truthy.\n";
}
?>
The above example prints:
False is truthy.
False is not truthy.

This function is for search a needle in a multidimensional haystack:
<?php
/**
 * A special function for search in a multidimensional array a needle
 *
 * @param mixed needle The searched variable
 * @param array haystack The array where search
 * @param bool strict It is or it isn't a strict search?
 *
 * @return bool
 **/
function in_array_r($needle, $haystack, $strict = false){
 foreach($haystack as $item){
  if(is_array($item)){
   if(in_array_r($needle, $item, $strict)){
    return true;
   }
  }else{
   if(($strict ? $needle === $item : $needle == $item)){
    return true;
   }
  }
 }
 return false;
}
?>

I needed a version of in_array() that supports wildcards in the haystack. Here it is:
<?php
function my_inArray($needle, $haystack) {
  # this function allows wildcards in the array to be searched
  foreach ($haystack as $value) {
    if (true === fnmatch($value, $needle)) {
      return true;
    }
  }
  return false;
}
$haystack = array('*krapplack.de');
$needle = 'www.krapplack.de';
echo my_inArray($needle, $haystack); # outputs "true"
?>
Unfortunately, fnmatch() is not available on Windows or other non-POSIX compliant systems.
Cheers,
Thomas

If array contain at least one true value, in_array() will return true every times if it is not false or null
Use strict = true
<?php
$arr = array(true);
in_array($any, $arr); // Will return true every time except null and false
?>

Kelvin's case-insensitive in_arrayi is fine if you desire loose typing, but mapping strtolower onto the array will (attempt to) cast all array members to string. If you have an array of mixed types, and you wish to preserve the typing, the following will work:
<?php
function in_array_ci($needle, array $haystack, $strict = false) {
  foreach ($haystack as $element) {
    if (gettype($needle) == 'string' && gettype($element) == 'string') {
      if (!strcasecmp($needle, $element)) {
        return true;
      }
    }
    elseif ($strict) {
      if ($needle === $element) {
        return true;
      }
    }
    else {
      if ($needle == $element) {
        return true;
      }
    }
  }
  return false;
}
?>