The workaround is to configure a property in the postgres database for the user, to make postgres behave as the old default.
ALTER USER username SET bytea_output = 'escape';
(or using the pgadmin interface)
(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)
pg_unescape_bytea — 取消 bytea 类型中的字符串转义
$data
) : stringpg_unescape_bytea() 将 bytea 数据类型中的字符串取消转义。返回未转义的字符串（二进制）。
Note:
当 SELECT bytea 类型，PostgreSQL 返回用 \ 前导的八进制字节值（例如 \032）。用户需要自行将其转换回二进制格式。
本函数需要 PostgreSQL 7.2 或更新版本。在 PostgreSQL 7.2.0 和 7.2.1 中，当激活了多字节支持时必须强制转换为 bytea 类型，例如
INSERT INTO test_table (image) VALUES ('$image_escaped'::bytea);。PostgreSQL 7.2.2 或更新版本不需要强制转换。例外是当客户端和后端的字符编码不匹配时，有可能出现多字节流错误。用户必须强制转换为 bytea 来避免此错误。
The workaround is to configure a property in the postgres database for the user, to make postgres behave as the old default.
ALTER USER username SET bytea_output = 'escape';
(or using the pgadmin interface)
PostgreSQL 9.0 introduced "hex" as the new default format for encoding binary data. Because "pg_unescape_bytea" only works with the old "escape" format, you need to do pg_query('SET bytea_output = "escape";'); before executing your select queries.
More details can be found here: http://www.postgresql.org/docs/9.0/static/datatype-binary.html
[Ed: Recent PostgreSQL versions support unescaping the "hex" format.]
<?php
$conexao = pg_connect("host=localhost dbname=name user=postgres password=123456") or die('Sorry =( : ' . pg_last_error());
$cod= $_GET['cod'];
$sql = "SELECT * FROM table WHERE cod_field = '$cod'";
$quer = pg_query($conexao, $sql);
$reg = pg_fetch_object($query);
print pg_unescape_bytea($reg -> field_bytea);
?>