Question

I have situation where I have a variable being used in some arithmetic (mostly just multiplication/division) in a PHP function. The variable is actually passed to the function from another. What gets passed, though, may be either a numerical value, or a string value.

So basically I have:

 $inverse = 1/$number;

Where $number may be either a valid number, or a string.

My question is what happens when $number is a string? How does php handle that situation?

Ultimately the answer isn’t too important; I can think of a couple of different ways of working around the situation. It’s just that it came up, I got curious, and a quick google search couldn’t answer my question. Even if I don’t need to know the answer, I’d like to know the answer, because understanding how PHP works will help me in the future.

Thanks.

Answer 1

PHP will perform type-coercion (also known as type-juggling) and attempt to interpret the value as a number when it is a string when the variable is used in a numerical context.

See the docs on the division operator:

The division operator (“/”) returns a float value unless the two
operands are integers (or strings that get converted to integers) and
the numbers are evenly divisible, in which case an integer value will
be returned.

Also relevant, String conversions to a number:

When a string is evaluated in a numeric context, the resulting value
and type are determined as follows.

….

The value is given by the initial portion of the string. If the string
starts with valid numeric data, this will be the value used.
Otherwise, the value will be 0 (zero). Valid numeric data is an
optional sign, followed by one or more digits (optionally containing a
decimal point), followed by an optional exponent. The exponent is an
‘e’ or ‘E’ followed by one or more digits.