Operators

PHP comes with a number of operators for working on your data, and they appear in Table A-1.

For example, here are the PHP math operators:

`+`	Adds two numbers
-	Subtracts one number from another
`*`	Multiplies two numbers together
`/`	Divides one number by another
`%`	Returns the remainder when one number is divided by another (modulus)

You can see them all at work in this example:

 <HTML>     <BODY>         <H1>Using the PHP math operators</H1>         <?php             echo "9 + 4 = ", 9 + 4;             echo "9 - 4 = ", 9 - 4;             echo "9 * 4 = ", 9 * 4;             echo "9 / 4 = ", 9 / 4;             echo "9 % 4 = ", 9 % 4;         ?>     </BODY> </HTML>

Operator precedence is also an issueif you evaluate this statement, what would be the result?

 <?php     echo 4 + 2 * 9; ?>

Will this be 4 + 2 * 9 = 6 * 9 = 54, or will the * be evaluated first, giving 4 + 2 * 9 = 4 + 18 = 22? In this case, you get 22 because the * operator has precedence over the + operator when you mix them up. Operator precedence, from highest to lowest, is shown in Table A-2.

Table A-2. Operators in Descending Order of Precedence
Operators
`new`
`[`
`! ~ ++ -- (int) (float) (string) (array) (object)`
`@`
`* / %`
`+ -.`
`<< >>`
`< <= > >=`
`== != === !==`
`&`
`^`
`\|`
`&&`
`\|\|`
`? :`
`= += -= *= /= .= %= &= \|= ^= <<= >>=`
`print`
`and`
`xor`
`or`
`,`

You can always use parentheses to tell PHP what to do if you're unsure about precedence. If you change this expression to (4 + 2) * 9, then you'll get 6 * 9 = 54:

 <?php     echo "4 + 2 * 9 = ", 4 + 2 * 9;     echo "(4 + 2) * 9", (4 + 2) * 9;     echo "4 + (2 * 9)", 4 + (2 * 9); ?>

Here, you'd get 22, 54, and 22.

Table A-2. Operators in Descending Order of Precedence