PHP中的正则表达式：强制第二次出现的单词

Question

I need to match a few urls for an application I'm working on;

So, I've got this reference string:

content/course/32/lesson/61/content/348

and I need a pattern that matches either

content

OR

content/course/[number]/lesson/[number]/content/[number]

What I've done so far is come up with this pattern:

$my_regex = "/content(\/?|(\/course\/\d{1,4}\/lesson\/\d{1,4}\/content\/\d{1,4}))$/";

which however has the following problem: This string returns a match which should otherwise not:

content/course/32/lesson/61/content

I'm thinking that it's got something to do with the word content repeating twice but I'm not entirely sure.

Any help is much appreciated.

Answer 1

The reason for the match is the alternation.

content\/?$

matches

content/course/32/lesson/61/content

To fix this, add a ^ (beginning of line) to the start of your regex to ensure the entire string is matched and not only the ending:

/^content(\/?|(\/course\/\d{1,4}\/lesson\/\d{1,4}\/content\/\d{1,4}))$/

See it in action