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Replacing 2 characters with with preg_replace

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Join Date: Oct 2007

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Venom Rush Venom Rush is offline

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Replacing 2 characters with with preg_replace

Jan 15th, 2008

Hi there

I'm using preg_replace to replace ' and " with a backslash in front of them so that I don't get problems with my MySQL INSERT queries. But at the moment I can only replace them with one charater as below:

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 php Syntax (Toggle Plain Text) 
$unedited = $_POST['content'];
$content = preg_replace("/['|\"]/", "\'", $unedited);
$unedited = $_POST['content'];
$content = preg_replace("/['|\"]/", "\'", $unedited);

At the moment that just replaces both ' and " with ' which isn't ideal. Can anyone tell me how I'd be able to replace them with the respective charater. (e.g. ' would be replaced with \' and " would be replaced with\")

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nav33n

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Re: Replacing 2 characters with with preg_replace

Jan 15th, 2008

Umm.. I am not sure about preg_replace. But you can do the same with str_replace!

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 php Syntax (Toggle Plain Text) 
<?php
$txt="' is a single quote \" is a double quote.I want to replace ' with \' and \" with \" ";
echo "Actual text: " .$txt."<br />";
$x=str_replace('"','\"',str_replace("'","\'",$txt));
echo "Replaced text: ". $x;
?>
<?php
$txt="' is a single quote \" is a double quote.I want to replace ' with \' and \" with \" ";
echo "Actual text: " .$txt."<br />";
$x=str_replace('"','\"',str_replace("'","\'",$txt));
echo "Replaced text: ". $x;
?>

Hope it helps!
Naveen

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Fungus1487 Fungus1487 is offline

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Re: Replacing 2 characters with with preg_replace

Jan 15th, 2008

you dont need str_replace inside str_replace etc etc.

use two arrays

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 PHP Syntax (Toggle Plain Text) 
$your_txt = "Hello 'WORLD'";
$txt = array("'", "\"");
$txt_replace = array("\'", "\\\"");
$x=str_replace($txt, $txt_replace, $your_txt);
echo $x;
$your_txt = "Hello 'WORLD'";
$txt = array("'", "\"");
$txt_replace = array("\'", "\\\"");
$x=str_replace($txt, $txt_replace, $your_txt);
echo $x;

this way you can have two arrays and no messy inner replacements inside replacements.

although nav33n may have shown you his way as at first it appears easier (both do the same trick).

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ShawnCplus ShawnCplus is offline

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Re: Replacing 2 characters with with preg_replace

Jan 15th, 2008

... I'm not entirely sure why'd you write your own function when the built-in addslashes function works perfectly well.

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Walkere

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Re: Replacing 2 characters with with preg_replace

Jan 15th, 2008

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Originally Posted by ShawnCplus

... I'm not entirely sure why'd you write your own function when the built-in addslashes function works perfectly well.

Aye, I was wondering the same thing.

addslashes() is slightly different - it escapes a couple of extra characters (including '\' and NUL). However, these (especially \) need to be escaped anyway.

So, to fill in the original example...

 Help with Code Tags 
 PHP Syntax (Toggle Plain Text) 
$unedited = $_POST['content'];
$content = addslashes($unedited);
$unedited = $_POST['content'];
$content = addslashes($unedited);

However, you might be looking to learn how to use preg_replace... so we'll go back to the original example.

You can use preg_replace() like Fungus did with str_replace - sending an array as the search and replacement parameters.

The problem with your example is that you're only presenting one thing for the replacement parameter - "\'".

In order to replace ' with \' and " with \" you need to do one of a few things - perform two preg_replaces (one for each replacement), use arrays within the preg_replace, or use a variable in the regex to print the quote based on what the search found. I'm not that good with regex, so I'm not sure if you can do that... but I think you can.

Anyhow, here's an example of how you could use arrays to perform the desired function with preg_replace.

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 PHP Syntax (Toggle Plain Text) 
$string = "\"You're not very wise,\" said the wise man.";
 
$string = preg_replace(array("/'/", '/"/'), array("\'", '\"'), $string);
echo $string;
$string = "\"You're not very wise,\" said the wise man.";

$string = preg_replace(array("/'/", '/"/'), array("\'", '\"'), $string);
echo $string;