Help with preg_replace

1. What is the difference between Str_replace and Preg_replace?
2. How does Preg_replace work in PHP?
3. How do you use pregReplace?
4. Is Preg_replace global?
5. What is RegEx replace?
6. What does this RegEx do?
7. What is the correct way of declaring PHP variable?
8. How do I match a string in PHP?
9. What is the difference between echo () and print () function?
10. Which function is used to replacing pattern in string?
11. What is the size limit for strings in PHP?
12. How remove all special characters from a string in PHP?

What is the difference between Str_replace and Preg_replace?

str_replace replaces a specific occurrence of a string, for instance "foo" will only match and replace that: "foo". preg_replace will do regular expression matching, for instance "/f. 2/" will match and replace "foo", but also "fey", "fir", "fox", "f12", etc.

How does Preg_replace work in PHP?

The preg_replace() function returns a string or array of strings where all matches of a pattern or list of patterns found in the input are replaced with substrings.
...
There are three different ways to use this function:

1. One pattern and a replacement string. ...
2. An array of patterns and a replacement string.

How do you use pregReplace?

The preg_replace() function returns an array if the subject parameter is an array otherwise it returns a string. After the replacement has done, the modified string will be returned. If any matches do not find, the string will remain unchanged.

Is Preg_replace global?

[fphp]preg_replace[/fphp] is global unless you specify the $limit parameter.

What is RegEx replace?

The Regex. Replace(String, String, MatchEvaluator, RegexOptions) method is useful for replacing a regular expression match if any of the following conditions is true: If the replacement string cannot readily be specified by a regular expression replacement pattern.

What does this RegEx do?

A regular expression (shortened as regex or regexp; also referred to as rational expression) is a sequence of characters that specifies a search pattern. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation.

What is the correct way of declaring PHP variable?

Rules for PHP variables:

• A variable starts with the $ sign, followed by the name of the variable.
• A variable name must start with a letter or the underscore character.
• A variable name cannot start with a number.
• A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )

How do I match a string in PHP?

preg_match() in PHP – this function is used to perform pattern matching in PHP on a string. It returns true if a match is found and false if a match is not found. preg_replace() in PHP – this function is used to perform a pattern match on a string and then replace the match with the specified text.

What is the difference between echo () and print () function?

echo and print are more or less the same. They are both used to output data to the screen. The differences are small: echo has no return value while print has a return value of 1 so it can be used in expressions. echo can take multiple parameters (although such usage is rare) while print can take one argument.

Which function is used to replacing pattern in string?

The REGEXREPLACE( ) function uses a regular expression to find matching patterns in data, and replaces any matching values with a new string.

What is the size limit for strings in PHP?

PHP's string length is limited by the way strings are represented in PHP; memory does not have anything to do with it. According to phpinternalsbook.com, strings are stored in struct char *val; int len; and since the maximum size of an int in C is 4 bytes, this effectively limits the maximum string size to 2GB.

How remove all special characters from a string in PHP?

function clean($string) $string = str_replace(' ', '-', $string); // Replaces all spaces with hyphens. $string = preg_replace('/[^A-Za-z0-9\-]/', '', $string); // Removes special chars. return preg_replace('/-+/', '-', $string); // Replaces multiple hyphens with single one.