PHP：转义非字母数字字符

Question

I'm trying to port a script that I wrote in bash some time ago into PHP. One particular line is about escaping all non-alphanumeric characters.

In bash, I was able to do it as a one-liner as follows:

echo "aaa bbb::" | sed 's/\([^a-zA-Z0-9]\)/\\\1/g'
# => aaa\ bbb\:\:

The closest I got in PHP was with this:

echo preg_replace('/([^a-zA-Z0-9])/','\\\','aaa bbb::');
# => aaa\bbb\\

However I'm struggling to reuse my regex group inside preg_replace (I tried \1 and $1).

Can someone help me get this PHP one-liner right please?

Answer 1

echo preg_replace('/([^a-zA-Z0-9])/',"\\\\$1",'aaa bbb::');
//output => aaa\ bbb\:\:

Answer 2

Use [^[:alnum:]] to represent all non-alphanumeric characters in your locale and don't forget to double-double escape your backslashes:

$ cat test.php
#!/usr/bin/env php

<?
echo preg_replace('/([^[:alnum:]])/', '\\\\$1', 'aaa bbb::');
?>

$ ./test.php 
aaa\ bbb\:\:

Answer 3

Try:

echo preg_replace('~([^a-zA-Z0-9])~', '\\\\$1', 'aaa bbb::');