PHP : couldn't replace using preg_replace()

Just I'm replacing the object tag in 开发者_C百科the given string

$matches = preg_replace("/<object(.+?)</object>/","replacing string",$str);

but it is showing the error as

Warning: preg_replace() [function.preg-replace]: Unknown modifier 'o'

What went wrong?

The slash in </object> has to be quoted: <\/object>, or else it is interpreted as the end of your regex since you're delimiting it with slashes. The whole line should read:

$matches = preg_replace("/<object(.+?)<\\/object>/","replacing string",$str);

In your regex the forward slash is the regex delimiter. As you are dealing with tags, better use another delimiter (instead of escaping it with a backslash):

$matches = preg_replace("#<object(.+?)</object>#", "replacing string", $str);

There are other delimiteres, too. You can use any non-alphanumeric, non-backslash, non-whitespace character. However, certain delimiters should not be used under any circumstances: |, +, * and parentheses/brackets for example as they are often used in the regular expressions and would just confuse people and make them hate you.

Btw, using regular expressions for HTML is a Bad Thing!

The first character is taken as delimiter char to separate the expression from the flags. Thus this:

"/[a-z]+/i"

... is internally split into this:

- Pattern: [a-z]+
- Flags: i

So this:

"/<object(.+?)</object>/"

... is not a valid regexp. Try this:

"@<object(.+?)</object>@"