REGULAR EXPRESSIONS

Regular Expressions

______ are patterns that are used for matching and manipulating strings according to specified rules

• POSIX Extended

• Perl Compatible Regular Expressions

PHP supports two types of regular expressions:

preg_match()

Pass to the _____ the regular expression pattern as the first argument and a string containing the text you want to search as the second argument

regular expression pattern

A ______ is a special text string that describes a search pattern

metacharacters

Regular expression patterns consist of literal characters and ______, which are special characters that define the pattern- matching rules

forward slash (/)

Regular expression patterns are enclosed in opening and closing delimiters. The most common character delimiter is the _____

period (.)

A ______ in a regular expression pattern specifies that the pattern must contain a value at the location of the _____

0, 1

A return value of __ indicates that the string does not match the pattern and __ if it does

anchor

An ____ specifies that the pattern must appear at a particular position in a string

^, $

The ___ metacharacter anchors characters to the beginning of a string. The ___ metacharacter anchors characters to the end of a string

backslash

To match any metacharacters as literal values in a regular expression, escape the character with a _____

quantifiers

Metacharacters that specify the quantity of a match are called _____

question mark (?)

A ______ quantifier specifies that the preceding character in the pattern is optional

addition(+)

The _____ quantifier specifies that one or more sequential occurrences of the preceding characters match

asterisk (*)

A ______ quantifier specifies that zero or more sequential occurrences of the preceding characters match

{ }

The____ quantifiers specify the number of times that a character must repeat sequentially

subexpression, subpattern

When a set of characters enclosed in parentheses are treated as a group, they are referred to as a _____ or ______

Character classes

_____ in regular expressions treat multiple characters as a single item

([])

Characters enclosed with the____ metacharacters represent alternate characters that are allowed in a pattern match

hyphen metacharacter (-)

The ______ specifies a range of values in a character class

^

The __ metacharacter (placed immediately after the opening bracket of a character class) specifies optional characters to exclude in a pattern match

|

The __ metacharacter is used to specify an alternate set of patterns

OR

The | metacharacter is essentially the same as using the ___ operator to perform multiple evaluations in a conditional expression

Pattern modifiers

_____ are letters placed after the closing delimiter that change the default rules for interpreting matches

• i

• m

• s

• o

• The pattern modifier, __, indicates that the case of the letter does not matter when searching

• The pattern modifier, __, allows searches across newline characters

• The pattern modifier, __, changes how the . (period) metacharacter works

• The pattern modifier, __, evaluates the expression only once

Character classes

_____ specify an entire range of characters, for example, the alphabet or an integer set

[[:alpha:]]

It matches any string containing alphabetic characters aA through zZ.

[[:digit:]]

It matches any string containing numerical digits 0 through 9.

[[:alnum:]]

It matches any string containing alphanumeric characters aA through zZ and 0 through 9

[[:space:]]

It matches any string containing a space.