php regex replace double backslash with single

Question

I do not want to use `stripslashes()` because I only want to replace "\" with "". I tried `preg_replace("/\\/", "\", '2\sin(\pi s)\Gamma(s)\zeta(s) = i\oint_C \frac{-x^{s-1}}{e^x -1} \mathrm{d}x');` Which to my disapointment returns: `2\sin(\pi s)\Gamma(s)\zeta(s) = i\oint_C \frac{-x^{s-1}}{e^x -1} \mathrm{d}x` Various online regex testers indicate that the above should work. Why is it not?

Accepted Answer

First, like many other people are stating, regular expressions might be too heavy of a tool for the job, the solution you are using should work however.

```
$newstr = preg_replace('/\\/', '\', $mystr);
```

Will give you the expected result, note that preg_replace returns a new string and does not modify the existing one in-place which may be what you are getting hung up on.

You can also use the less expensive str_replace in this case:

```
$newstr = str_replace('\\', '\', $mystr);
```

This approach costs much less CPU time and memory since it doesn't need to compile a regular expression for a simple task such as this.

php regex replace double backslash with single

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