PHP preg_match pattern issue

Question

I am trying to make this pattern work correctly and I just can't make it work it out. Basically, i want to validate a string that can only accept letter, numbers and the following characters: @!?_;:-,.

Here is the source code I have so far:

<?php
  $test_string = '1234bcd@!?_;:-,.';
  echo preg_match( "/^[a-z0-9@!?_;:,.]{4,12}$/i", $test_string );
?>

And the question is? By the way, the result of these two lines will be 0, as your $test_string is too long: the pattern will match only if the tested string's length is between 4 and 12. — raina77ow
– raina77ow, Commented Oct 3, 2012 at 13:57

nickb · Accepted Answer · 2012-10-03 14:03:40Z

2

You're trying to print an integer, which won't achieve what you're trying to do. Try this:

if( preg_match( "/^[a-z0-9@!?_;:,.]{4,12}$/i", $test_string )) {
    echo 'valid string!';
} else {
    echo 'invalid!';
}

Note that your regex deems strings to be valid if they are:

Between 4 and 12 characters long
Consist of only alpabetic characters, numbers, and the other characters you've included.

Also note that your input string is supposed to be invalid, not only because it is too long, but because it contains a dash, which is not supported by your regex:

1234bcd@!?_;:-,.
             ^
             No match

To include it in your regex, place it at the end of your character class in the regex:

preg_match( "/^[a-z0-9@!?_;:,.-]{4,12}$/i", $test_string )
                              ^

edited Oct 3, 2012 at 14:03

answered Oct 3, 2012 at 13:57

nickb

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4 Comments

raina77ow Over a year ago

Somehow I think the question is not about replacing 0 and 1 with something more meaningful. Yet I may be wrong, of course. )

nickb Over a year ago

That was my interpretation of the question :) Although it is a tad vague, so who knows!

macino Over a year ago

escape the - in character class

nickb Over a year ago

@Macino - No, you don't need to, it's at the end of the character class (for a reason).

macino · Accepted Answer · 2012-10-03 13:59:56Z

0

some of the characters are reserved by regexp such as . ? etc. use them with backslashes

if( preg_match( "/^[a-z0-9@!\?_;:,\.\-]{4,12}$/i", $test_string )) {  
  ...
}

answered Oct 3, 2012 at 13:59

macino

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2 Comments

nickb Over a year ago

That's not the case when they're in a character class.

macino Over a year ago

for the ? and . yes but not for the - . It's just good habit to escape these everywhere (but as you mentioned, not necessary unles they are \ ^ - ]). look at php doc.

Anthony Simmon · Accepted Answer · 2012-10-03 14:10:04Z

0

This pattern works :

$test_string = '1234bcd@!?_;:-,.';

if(preg_match('/^[a-z0-9@!\?_;:,\.\-]{4,12}$/i', $test_string))
{
    echo 'Valid';
}

But in this case 1234bcd@!?_;:-,., it won't because the input string length is 16 (not between 4 and 12 characters long).

By the way, always escape meta-characters. You will find the complete list here.

answered Oct 3, 2012 at 14:10

Anthony Simmon

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