How do I search for a text in a .txt file?

[leaven]

Hi,

I've used php to create a .txt file on the user's computer. Now I would like php to search for a specific text in that .txt file and place it into a variable.
Also I'd like to have php overwrite that piece of text with another text in this .txt file.

Example:

the text file contains the text "permission = 2100"
I want php to look for this text and put the value of 2100 to a variable called $permission_old.
Then I have another variable called $permission_new that contains the value 2200.
PHP must now write the value of $permission_new to the txt file so that it says "permission = 2200", and replace the text "permission = 2100" !!
PHP should just generate an error message when the text that is searched for is not found.

What is the best way to get this done?

[Yegg]

if U need 2 change just number, and don't know what this number is, but U know that it's integer from 4 digits U can use irregular expression functions, but NOT EREG_REPLACE, they R slow as elefant!!!!, only perl library based......
$new_var=preg_replace("/\d{4}/m", $var_2_replace_with, $var_where_make_replacement); well, try I cannot to check now if this syntaxis RIGHT.

[chrisleon]

I have also been trying to figure this out. Have you found anything that is usefull, or are you still jammed up.

[intenz]

$strWord = 'foo';
$strWord2 = 'foo2';
$arrFile = file('file.txt');
for($i = 0; $i < count($arrFile); $i++)
{
	if(strstr($arrFile[$i],$strWord))
		$strTheOne = str_replace($strWord,$strWord2,$arrFile[$i]);
}