PHP gmp_scan1() function

As of my last update in September 2021, PHP’s GMP (GNU Multiple Precision) extension includes the gmp_scan1() function. This function is used to scan for the first one bit (set bit) in a GMP number, starting from the least significant bit (LSB) position.

Here’s the syntax of the gmp_scan1() function:

int gmp_scan1 ( GMP $num , int $start )

Parameters:

• $num: The GMP number to scan for one bits.
• $start: The starting bit position for scanning. If provided, the function will start scanning from this bit position. If omitted, it starts scanning from the LSB position (bit 0).

Return value:

• The gmp_scan1() function returns the index of the first one bit (counting from 0) found in the GMP number. If no one bit is found, it returns -1.

Example:

$number = gmp_init('13'); // Binary: 1101

$oneBitIndex = gmp_scan1($number);
echo "The index of the first one bit is: " . $oneBitIndex; // Output: The index of the first one bit is: 0

In this example, the GMP number 13 (binary 1101) is scanned for the first one bit, starting from the LSB position (bit 0). The first one bit is found at index 0, and thus the function returns 0.

The gmp_scan1() function can be useful in various bitwise operations and can help in efficiently searching for specific bit patterns or performing bitwise manipulations on large integers.

As always, ensure that the GMP extension is enabled in your PHP configuration to use this function. Additionally, the availability of functions may change in newer PHP versions, so always refer to the PHP manual for the specific version you are using.