What does the warning "number_format() expects parameter 1 to be double, string given" indicate in PHP?

The warning "number_format() expects parameter 1 to be double, string given" indicates that the function number_format() is expecting a double data type as its first parameter, but it is receiving a string instead. To solve this issue, you need to ensure that the parameter passed to number_format() is of type double. You can use the floatval() function to convert a string to a double before passing it to number_format().

// Incorrect usage causing the warning
$number = "12345.67";
$formatted_number = number_format($number, 2);

// Correct way to fix the issue
$number = "12345.67";
$double_number = floatval($number);
$formatted_number = number_format($double_number, 2);