Regular expression in php with examples
What is a Regular Expression?A regular expression is a sequence of characters that forms a search pattern. When you search for data in a text, you can use this search pattern to describe what you are searching for. Show
A regular expression can be a single character, or a more complicated pattern. Regular expressions can be used to perform all types of text search and text replace operations. SyntaxIn PHP, regular expressions are strings composed of delimiters, a pattern and optional modifiers. In the example above, The delimiter can be any character that is not a letter, number, backslash or space. The most common delimiter is the forward slash (/), but when your pattern contains forward slashes it is convenient to choose other delimiters such as # or ~. Regular Expression FunctionsPHP provides a variety of functions that allow you to use regular expressions. The
Using preg_match()The ExampleUse a regular expression to do a case-insensitive search for "w3schools" in a string: $str = "Visit W3Schools"; Try it Yourself » Using preg_match_all()The ExampleUse a regular expression to do a case-insensitive count of the number of occurrences of "ain" in a string: $str = "The rain in SPAIN falls mainly on the plains."; Try it Yourself » Using preg_replace()The ExampleUse a case-insensitive regular expression to replace Microsoft with W3Schools in a string: $str = "Visit Microsoft!"; Try it Yourself » Regular Expression ModifiersModifiers can change how a search is performed.
Regular Expression PatternsBrackets are used to find a range of characters:
MetacharactersMetacharacters are characters with a special meaning:
QuantifiersQuantifiers define quantities:
Note: If your expression needs to search for one of the special characters you can use a backslash ( \ ) to escape them. For example, to search for one or more question marks you can use the following expression: $pattern = '/\?+/'; GroupingYou can use parentheses ExampleUse grouping to search for the word "banana" by looking for ba followed by two instances of na: $str = "Apples and bananas."; Try it Yourself » Complete RegExp ReferenceFor a complete reference, go to our Complete PHP Regular Expression Reference. The reference contains descriptions and examples of all Regular Expression functions. What is the regular expression in PHP?A regular expression is a sequence of characters that forms a search pattern. When you search for data in a text, you can use this search pattern to describe what you are searching for. A regular expression can be a single character, or a more complicated pattern.
What is regular expression with example?Solution: As we know, any number of a's means a* any number of b's means b*, any number of c's means c*. Since as given in problem statement, b's appear after a's and c's appear after b's. So the regular expression could be: R = a* b* c*
What is regular expression and quantifiers in regex in PHP?The {n,m} quantifier matches its preceding element at least n times, but no more than m times, where n and m are zero or a positive integer. For example, the regular expression '/\d{1,}-\d{1,}-\d{1,}/' also matches 1000-1000-2020 .
What does '$' mean in regex?$ means "Match the end of the string" (the position after the last character in the string).
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