pg_escape_bytea()

(PHP 4 >= 4.2.0, PHP 5, PHP 7)

转义 bytea 类型的二进制数据

说明

pg_escape_bytea(string $data): string

pg_escape_bytea()转义 bytea 数据类型的二进制字符串，返回转义后的字符串。

Note:
当对 bytea 类型字段进行 SELECT 操作时，PostgreSQL 返回前导的八进制字节值（例如032）。用户需要自己将结果转换为二进制格式。
本函数需要 PostgreSQL 7.2 或以上版本。在 PostgreSQL 7.2.0 和 7.2.1 版中，如果使用了多字节支持，bytea 类型必须被强制转换。例如INSERT INTO test_table(image)VALUES('$image_escaped'::bytea);。PostgreSQL 7.2.2 或以上版本不需要强制转换。异常情况是当客户端和后端字符编码不匹配时，可能会有多字节流错误。用户必须强制转换 bytea 以避免此错误。

参见pg_unescape_bytea()和pg_escape_string()。

The reason pg_unescape_bytea() do not exactly reproduce the binary data created by pg_escape_bytea() is because the backslash \ and single quote ' are double escaped by the pg_escape_bytea() function. This will lead to image seems corrupted when retrieve from the bytea field. The proper way to escape&unescape a binary string into a PG bytea field as follow:
<?php
$escaped_data = str_replace(array("\\\\", "''"), array("\\", "'"), pg_escape_bytea($data));
/* and later unescape the escaped data from the bytea field with following to get the original binary data */
$original_data = pg_unescape_bytea($escaped_data));
?>
more details at: http://archives.postgresql.org/pgsql-php/2007-02/msg00014.php

To prevent any problems with encoding you could use hexadecimal or base64 input to save and retrieve data to the database:
<?php 
 // Connect to the database
 $dbconn = pg_connect( 'dbname=foo' );
 
 // Read in a binary file
 $data = file_get_contents( 'image1.jpg' );
 
 // Escape the binary data
 $escaped = bin2hex( $data );
 
 // Insert it into the database
 pg_query( "INSERT INTO gallery (name, data) VALUES ('Pine trees', decode('{$escaped}' , 'hex'))" );
 // Get the bytea data
 $res = pg_query("SELECT encode(data, 'base64') AS data FROM gallery WHERE name='Pine trees'"); 
 $raw = pg_fetch_result($res, 'data');
 
 // Convert to binary and send to the browser
 header('Content-type: image/jpeg');
 echo base64_decode($raw);
?>

PostgreSQL 9.0 introduced a new hexadecimal-based representation for bytea data that is preferred over the escaping mechanism implemented by this function.
<?php
function pg_escape_byteahex($binary)
{
  return "E'\\\\x".bin2hex($binary)."'";
}
?>

to unescape_bytea use stripcslashes(). If you need to escape bytea and don't have pg_escape_bytea() function then use:
<?php
function escByteA($binData) {
 /**
  * \134 = 92 = backslash, \000 = 00 = NULL, \047 = 39 = Single Quote
  *
  * str_replace() replaces the searches array in order. Therefore, we must
  * process the 'backslash' character first. If we process it last, it'll
  * replace all the escaped backslashes from the other searches that came
  * before.
  */
 $search = array(chr(92), chr(0), chr(39));
 $replace = array('\\\134', '\\\000', '\\\047');
 $binData = str_replace($search, $replace, $binData);
 return $binData;
 //echo "<pre>$binData</pre>";
 //exit;
}
?>

using pg_escape_bytea without 'E' escape tag
<?php 
 // Die Binärdaten maskieren
 $escaped = pg_escape_bytea($data);
 // und in die Datenbank einfügen (falsch/wrong)
 pg_query("INSERT INTO gallery (name, data) VALUES ('Pine trees', E'$escaped')");
 // und in die Datenbank einfügen (richtig/right)
 pg_query("INSERT INTO gallery (name, data) VALUES ('Pine trees', '$escaped')");
?>

If you're getting errors about nonstandard use of \\ in a string literal, then you need to escape the encoded bytea as follows:
<?php
$escaped = pg_escape_bytea($data);
pg_query("INSERT INTO gallery (name, data) VALUES ('Pine trees', E'$escaped'::bytea)");
?>

if you need to change back bytea from the db to normal data, this will do that:
<?php
function pg_unescape_bytea($bytea) {
return eval("return \"".str_replace('$', '\\$', str_replace('"', '\\"', $bytea))."\";");
}
// use like this
$rs = pg_query($conn, "SELECT image from images LIMIT 1");
$image = pg_unescape_bytea(pg_fetch_result($rs, 0, 0));
?>
/Tobias