how to check if string contains square brackets php

Question

I have a strange question maybe you could help me with. I am trying to check whether the given string contains special characters. The code below is working however one character seems to get exempted on the condition which is the square brackets [ ]. Can you help me with this? thank you.

    $string = 'starw]ars';

    if (preg_match('/[\'^£$%&*()}{@#~?><>,|=_+¬-]/', $string)) {
        echo 'Output: Contains Special Characters';
    }else{
        echo 'Output: valid characters';
    }

Please note: I can't use below condition since I need to accept others characters from other languages like in arabic, chinese, etc. so it means I need to specify all characters that is not allowed.

    if (!preg_match('/[^A-Za-z0-9]/', $string))

Appreciate your help. Thanks.

Answer 1

You should add escaped square brackets to your expression.

preg_match('/[\'^£$%&*()}{@#~?><>,|=_+¬-\[\]]/', $string)

EDIT: Apologies to @Thamilan, I didn't see your comment.

EDIT 2: You could also use the preg_quote function.

preg_match(preg_quote('\'^£$%&*()}{@#~?><>,|=_+¬-[]', '/'), $string);

The preg_quote function will escape your special characters for you.

Answer 2

Use strpos:

$string = 'starw]ars';

if (strpos($string, ']') !== false) {
    echo 'true';
}

Please see the following answer for additional information: How do I check if a string contains a specific word in PHP?

Answer 3

You forgot to add square brackets [] in your expression. I have added this \[\] in your current expression.

Try this code snippet here

<?php

ini_set('display_errors', 1);

$string = 'starw]ars';

if (preg_match('/[\[\]\'^£$%&*()}{@#~?><>,|=_+¬-]/', $string))
{
    echo 'Output: Contains Special Characters';
} else
{
    echo 'Output: valid characters';
}

Answer 4

Try this example:

<?php
$string = 'starw]]$%ars';
if (preg_match('/[\'\/~`\!@#\$%\^&\*\(\)_\-\+=\{\}\[\]\|;:"\<\>,\.\?\\\]/', $string))
{
    echo 'Output: Contains Special Characters';
} else
{
    echo 'Output: valid characters';
}
?>

Output:

Output: Contains Special Characters