what are these regex expressions meaning?

1. preg_match( '/<title>(.*)<\/title>/',.....)

开发者_如何学运维

2. preg_match("/src=[\"']?([^\"']?.*(png|jpg|gif))[\"']?/i",....)

The first is to extract the contents from a HTML title tag.

The second is to extract images' src attributes from a HTML document, but is very imperfect (It won't catch references to image resources that end in .jpeg or have no extension at all).

Regular expressions are not a good idea for parsing HTML! One should use a HTML parser instead. They are far from fireproof.

1) Matches anything between <title> and </title> a la an HTML page's title, so run against <title>foo</title> results in the match being foo.

2) Matches any string following src= that ends in png, jpg or gif. Used to extract the URL of images in HTML code.

Per @Pekka's answer: don't do this in real world code.