Use of PHP built-in functions

PHP built-in functions provide the following functions: 1. Type conversion: is_numeric(), floatval(), strval(), intval(); 2. String processing: strlen(), substr(), ucwords(), strtolower(); 3. Array processing: count(), in_array(), array_merge(), array_filter(); 4. Mathematical functions: round(), pow(), sqrt(), max(); 5. Date and Time functions: time(), date(), strtotime(), mktime(). Practical example: The code snippet uses the filter_var() function to verify the validity of an email address.

Usage of PHP built-in functions

PHP built-in functions are predefined functions that can be used for various purposes without user definition. operate. They provide powerful features that simplify programming tasks and increase code reusability.

Type conversion function

• is_numeric(): Check whether the variable is a number.
• floatval(): Convert the variable to a floating point number.
• strval(): Convert the variable to a string.
• intval(): Convert a variable to an integer.

String processing function

• strlen(): Returns the length of the string.
• substr(): Extract a substring from a string.
• ucwords(): Capitalize the first letter of the words in the string.
• strtolower(): Convert the string to lowercase.

Array processing function

• count(): Returns the number of elements in the array.
• in_array(): Check whether an element exists in the array.
• array_merge(): Merge two or more arrays.
• array_filter(): Filter elements that meet specific conditions from the array.

Mathematical functions

• round(): Rounds a number to the specified number of digits.
• pow(): Calculate the power of a number.
• sqrt(): Calculates the square root of a number.
• max(): Returns the maximum of two or more numbers.

Date and time functions

• time(): Get the current timestamp.
• date(): Format the timestamp into a date and time string.
• strtotime(): Parses date and time strings into timestamps.
• mktime(): Creates a timestamp based on the specified date and time parameters.

Practical Case: Validating User Input

The following code uses a built-in function to validate the email address entered by the user:

$email = 'john@example.com';

if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
  echo '无效的电子邮件地址';
} else {
  echo '有效的电子邮件地址';
}

This code The snippet uses the filter_var() function to verify that $email is a valid email address and outputs the message accordingly.

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