Allow Only One Hyphen with a Literal String

[equipment]

How could this be achieved with preg_match?

 

It should be solely alphabetic (lower case) with no special characters and only one hyphen should be allowed.

[MMDE]

Please tell us how you would like to use this?

 

Is there input from the user by post data for example?

 

if(preg_match_all('/-/', $the_string, $matches)<2){

}

The manual says you only need two parameters for preg_match_all, and that you don't need to give a $matches parameter, but my server sure didn't like that, maybe yours do?

[equipment]

Well it is just like that, it is for inputted data through an input field, simply a literal string with maximum one hyphen should be allowed not more, solely alphabetic with no special characters.

 

I just have problems wrapping my head around preg_match

 

example-string

[xyph]

<?php

$string = 'some----string---with-hyphens----';

$new_string = preg_replace('/-+/', '-', $string);

echo $new_string; // some-string-with-hyphens-

?>

[equipment]

xyph,

 

that is a good starting point, how can I now add the following conditions to only have?

 

1. only lower case letters are possible

2. no other special characters, including white space are possible

3. and only one hyphen is possible

[ManiacDan]

When confronted with a problem like this, it's often a good idea to take a step back and ask WHY you only want one hyphen.  What purpose does that serve?

 

However, this regex solves your issue without asking why:

/(^-[a-z]+$)|(^[a-z]+-[a-z]+$)|(^[a-z]-$)/

 

Also, in the future, please describe the whole problem.  Xyph answered your question in its entirety, and then you came back and said "that's a good start, now here's two more rules." 

[equipment]

Double post.

[equipment]

  Xyph answered your question in its entirety, and then you came back and said "that's a good start, now here's two more rules."

 

I outlined the rules clearly in the first post:

It should be solely alphabetic (lower case) with no special characters and only one hyphen should be allowed.

 

And then I wrote an example like this, before xyph would post:

 

example-string

 

To make you understand that in marketers terms, I want to build a tag system which should only accept this:

example-string

 

And that is enough one needs to know, simply enough to know, simply enough to know, simply enough to know, simply enough to know, simply enough to know.

[.josh]

pure regex:

 

if ( preg_match('~^[a-z]*-?[a-z]*$~',$string) ) {
  // valid
} else {
  // invalid
}

 

blended...may possibly be a little faster:

 

if  ( (substr_count($string,"-")<=1) &&  (preg_match('~^[a-z-]$~',$string)) )  {
  // valid
} else {
  // invalid
}

[ManiacDan]

Josh, is your regex faster than mine?  Just wondering.  Conditional regexes have always thrown me, despite being an 'expert' otherwise.

[.josh]

Numbers calculated using this benchmarking function.

 

Round 1:

times executed (each): 250000
fastest to slowest:
Array
(
    [josh_pure] => 0.00000539963519708157
    [ManiacDan] => 0.0000057829462635701
    [josh_blended] => 0.0000060079560636085
)
biggest difference time: 0.00000060832086652693
fastest is 11.266% faster than the slowest

 

Round 2:

times executed (each): 250000
fastest to slowest:
Array
(
    [josh_pure] => 0.00000552566420531364
    [ManiacDan] => 0.00000584143936571746
    [josh_blended] => 0.00000610485283878271
)
biggest difference time: 0.00000057918863346907
fastest is 10.4818% faster than the slowest

 

Round 3:

times executed (each): 250000
fastest to slowest:
Array
(
    [josh_pure] => 0.00000537841102728821
    [ManiacDan] => 0.00000559228
    [josh_blended] => 0.00000604077199996
)
biggest difference time: 0.00000066236097267179
fastest is 12.3152% faster than the slowest

18165_.txt

[ManiacDan]

Nice, thanks.