Built-in Functions

PHP provides many built-in functions that simplify common programming tasks.

These functions are grouped into categories such as:

• String Functions
• Array Functions
• Math Functions
• Date/Time Functions

String functions

String functions help manipulate and analyze text.

Common functions include:

• strlen() – get string length
• strpos() – find position of a substring
• str_replace() – replace text
• substr() – extract part of a string

Example

$text = "Hello World";

echo strlen($text);

Replace Text

echo str_replace("World", "PHP", "Hello World");

Array functions

Array functions allow working with collections of values.

Common functions include:

• count()
• array_push()
• array_merge()
• array_map()

Example

$numbers = [1,2,3];

echo count($numbers);

Adding Values

array_push($numbers, 4);

print_r($numbers);

Math functions Math functions perform mathematical calculations.

Common functions include:

• abs() – absolute value
• round() – round numbers
• sqrt() – square root
• rand() – generate random numbers

Example

echo abs(-10);

Random Number

echo rand(1, 100);

Date and time functions

Date and time functions work with timestamps and formatted dates.

Common functions include:

• date()
• time()
• strtotime()

Example

echo date("Y-m-d");

Current Timestamp

echo time();