如何获得前一年的PHP？

I've a format date like this

$y = date('Y');

so the output is 2015

but if I try getting previous year using the below code:

$yr = date('Y'($y,'-1 year'));
echo $yr;

I get incorrect output. The output is 1970.

How to get the previous year?

You aren't using any library which does natural language processing. A better option will be to do

$y = date('Y') - 1;

Also, I am worried about the syntax: date('Y'($y...

EDIT

Exactly as I expected, your code doesn't even compile: Parse error: syntax error, unexpected '(' in /scratchpad/index.php on line 3

Try creating a function which does this:

function getYear( $before = 0 ) {

    return ( date( 'Y' ) - $before );

}

Even better is to use strtotime:

function getYear( $context ) {

    return date( 'Y', strtotime( $context ) );

}

Then use it something like:

echo ( getYear( '-1 year' ) );

will give: 2014.

Try using strtotime function

<?php
 echo date('Y', strtotime('-1 Year'));
?>