How do I remove alphanumeric characters from a text file in PHP?

Question

I have a huge text file, and I want to remove everything that isn't a symbol (for example - , . ' "), how do I remove everything so that the only things that are left is symbols, without specifying what symbols to keep.

As an example

"There's a man outside. He's come to take you away!"

would leave you with "'.'!"

You are looking for http://www.php.net/manual/en/function.preg-replace.php — Kyslik, Jun 06 '13 at 12:51
Duplicate of question [Removing Non Alphanumeric Characters With PHP](http://stackoverflow.com/questions/659025/removing-non-alphanumeric-characters-with-php?rq=1) (Just the other way around) — Overv, Jun 06 '13 at 12:52
Duplicate: [Need to remove all AlphaNumeric characters from an array](http://stackoverflow.com/q/9408808/938236) — Francisco Presencia, Jun 06 '13 at 12:52
So.... do accented characters count as alphanumeric or symbols? — Spudley, Jun 06 '13 at 12:54
@Spudley , and what about the ñ? Here in Spain that's a letter. But then, α is used as a symbol in Mathematics and as a letter in Greek — Francisco Presencia, Jun 06 '13 at 12:56

score 2 · Answer 1 · answered Jun 06 '13 at 12:51

2

Use regular expressions:

$outputText = preg_replace('/[a-z0-9]+/Ui', '', $inputText);

answered Jun 06 '13 at 12:51

SteeveDroz

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What is the difference between preg_replace and str_replace? Is it better practice to use one over the other? – Dave Melia Jun 06 '13 at 13:26
with `preg_replace`, you can use regular expressions. If you don't know what a RegEx is, I suggest you to find out, for it is way more powerfull than simple text search and replace, by far. http://www.regular-expressions.info/tutorial.html – SteeveDroz Jun 06 '13 at 13:32

score 1 · Answer 2 · answered Jun 06 '13 at 12:51

1

preg_replace("/[A-Za-z0-9+]/", '', $string);

answered Jun 06 '13 at 12:51

Mohammad Masoudian

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score 0 · Answer 3 · answered Jun 06 '13 at 12:51

0

Try this (untested, just freestyled into this window here):

implode('', array_filter(str_split([.. your string ..]), function ($char) { return !ctype_alnum($char); }));

answered Jun 06 '13 at 12:51

Christian Kiewiet

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score 0 · Answer 4 · answered Jun 06 '13 at 13:36

0

I went with

$symbCount = preg_replace('/[A-Za-z0-9+]/', '', $fileStr);

Thanks

answered Jun 06 '13 at 13:36

Dave Melia

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How do I remove alphanumeric characters from a text file in PHP?

4 Answers4