Remove control characters from PHP string


Question

How can I remove control characters like STX from a PHP string? I played around with

preg_replace("/[^a-zA-Z0-9 .\-_;!:?äÄöÖüÜß<>='\"]/","",$pString)

but found that it removed way to much. Is there a way to remove only control chars?

1
57
3/5/2018 12:40:48 AM

Accepted Answer

If you mean by control characters the first 32 ascii characters and \x7F (that includes the carriage return, etc!), then this will work:

preg_replace('/[\x00-\x1F\x7F]/', '', $input);

(Note the single quotes: with double quotes the use of \x00 causes a parse error, somehow.)

The line feed and carriage return (often written \r and \n) may be saved from removal like so:

preg_replace('/[\x00-\x09\x0B\x0C\x0E-\x1F\x7F]/', '', $input);

I must say that I think Bobby's answer is better, in the sense that [:cntrl:] better conveys what the code does than [\x00-\x1F\x7F].

WARNING: ereg_replace is deprecated in PHP >= 5.3.0 and removed in PHP >= 7.0.0!, please use preg_replace instead of ereg_replace:

preg_replace('/[[:cntrl:]]/', '', $input);
96
2/9/2018 7:47:37 AM

For Unicode input, this will remove all control characters, unassigned, private use, formatting and surrogate code points (that are not also space characters, such as tab, new line) from your input text. I use this to remove all non-printable characters from my input.

<?php
$clean = preg_replace('/[^\PC\s]/u', '', $input);

for more info on \p{C} see http://www.regular-expressions.info/unicode.html#category


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