99 bottles

min.php

# 208 bytes
$b=99;$d=" bottles of beer";$c="$d on the wall";do{echo "$b$c, $b$d.\n";if(!--$b){echo "Go to the store and buy some more";$b=99;}else echo "Take one down and pass it around";echo ", $b$c.\n\n";}while($b<99);

non-min.php

<?php
$b=99;
$d=" bottles of beer";
$c="$d on the wall";
do{
    echo "$b$c, $b$d.\n";
    if(!--$b){
        echo "Go to the store and buy some more";$b=99;
    }
    else echo "Take one down and pass it around";
    echo ", $b$c.\n\n";
}while($b<99);