php - How I can check if a string contais "x" but not "xy"

How can I check if a string contains "x" but not "xy"?

So I have strings like this:

"5103564-XY",
"77-546-00X",
"292196232",
"5102200X",
"5102205",

"5102251-EP".
...

I only need the numbers which have the letter "x" at the end. Can Someone help me to realize that in PHP?

So if I try this:

$strings = array("5103564-AD", "77-546-00D", "292196232", "5102200D", "5102205", "5102251-EP");
print_r(preg_grep('/d$/i', $strings));

So the output is this:

Array
(
    [0] => 5103564-AD
    [1] => 77-546-00D
    [3] => 5102200D
)

But this is not the wished result. I Only need the strings, which contains only the letter "D" and not the strings, which contains "AD" or somethingelse too. I hope it is now a little bit clearer, what I need/mine.

Answer

Use preg_grep to find only values in the list which end in just a d or D (with no preceding letter):

$strings = array("5103564-AD", "77-546-00D", "292196232", "5102200D", "5102205", "5102251-EP");
print_r(preg_grep('/[^a-z]d$/i', $strings));

Output:

Array ( 
    [1] => 77-546-00D
    [3] => 5102200D
)

Demo on 3v4l.org