How do you convert a string to an integer in PHP?

The function that efficiently converts a string to an integer in PHP is the intval() function. This function takes a variable as its argument and returns its integer value. When a string is passed to intval(), PHP automatically handles the conversion, interpreting the leading numerical characters in the string until it encounters a non-numeric character. If the string does not contain any numbers, intval() will return 0.

The correct operation of intval() is essential for various applications where developers need to ensure that strings representing numeric values are treated as integers in calculations or operations, thereby avoiding errors that might arise from type coercion in arithmetic contexts.

In contrast, other options like str_to_int, int_cast, and convert() do not exist in PHP as valid built-in functions for converting strings to integers, making them invalid choices. This showcases the importance of understanding PHP's built-in functions and their respective usage, as it allows developers to write more efficient and correct code.