php regex for number that is 4 characters

After that we will introduce you wih regular expression related functions. Lets give explanation for few concepts being used in PERL regular expressions. In fact, you can use any of the quantifiers introduced in the previous POSIX section. The POSIX syntax can be used almost interchangeably with the Perl-style regular expression functions. Perl-style regular expressions are similar to their POSIX counterparts. The sql_regcase() function can be thought of as a utility function, converting each character in the input parameter string into a bracketed expression containing two characters.

The spliti() function operates exactly in the same manner as its sibling split(), except that it is not case sensitive. The split() function will divide a string into various elements, the boundaries of each element based on the occurrence of pattern in string. The eregi_replace() function operates exactly like ereg_replace(), except that the search for pattern in string is not case sensitive. The eregi() function searches throughout a string specified by pattern for a string specified by string. The ereg_replace() function searches for string specified by pattern and replaces pattern with replacement if found. The ereg() function searches a string specified by string for a string specified by pattern, returning true if the pattern is found, and false otherwise. PHP currently offers seven functions for searching strings using POSIX-style regular expressions − Sr.No It matches any string containing a space. It matches any string containing alphanumeric characters aA through zZ and 0 through 9. It matches any string containing numerical digits 0 through 9. It matches any string containing alphabetic characters aA through zZ. Character classes specify an entire range of characters, for example, the alphabet or an integer set − Sr.No It matches any string containing a p followed by zero or more instances of the sequence php.įor your programming convenience several predefined character ranges, also known as character classes, are available. It matches any string enclosed within and.

It matches any string containing exactly two characters. It matches any string containing p, followed by any character, in turn followed by another p. It matches any string not containing any of the characters ranging from a through z and A through Z. It matches any string with p at the beginning of it.įollowing examples will clear your concepts about matching characters. It matches any string with p at the end of it. It matches any string containing a sequence of at least two p's. It matches any string containing a sequence of two or three p's. It matches any string containing a sequence of N p's It matches any string containing zero or one p's. It matches any string containing zero or more p's. It matches any string containing at least one p. The +, *, ?,, and $ flags all follow a character sequence. Each special character having a specific connotation. The frequency or position of bracketed character sequences and single characters can be denoted by a special character. The ranges shown above are general you could also use the range to match any decimal digit ranging from 0 through 3, or the range to match any lowercase character ranging from b through v. It matches any character from lowercase a through uppercase Z. It matches any character from uppercase A through uppercase Z. It matches any character from lower-case a through lowercase z. It matches any decimal digit from 0 through 9. They are used to find a range of characters. Bracketsīrackets () have a special meaning when used in the context of regular expressions. After that we will introduce you with regular expression related functions. Lets give explanation for few concepts being used in POSIX regular expression. The simplest regular expression is one that matches a single character, such as g, inside strings such as g, haggle, or bag. The structure of a POSIX regular expression is not dissimilar to that of a typical arithmetic expression: various elements (operators) are combined to form more complex expressions.

You can use any of them based on your comfort. PHP offers functions specific to two sets of regular expression functions, each corresponding to a certain type of regular expression.

Using regular expression you can search a particular string inside a another string, you can replace one string by another string and you can split a string into many chunks. They provide the foundation for pattern-matching functionality. Regular expressions are nothing more than a sequence or pattern of characters itself.

Php regex for number that is 4 characters