[eluser]sophistry[/eluser]
sorry! i couldn't resist.
i benchmarked this at around 20% faster with small strings; there's no need to go into array land at all.
this will stay fast even if the input string $content is huge while the array functions will begin to bog down (even with the limit param of explode()).
Code:
$findme = '<|more|>';
$small = substr($content, 0, strpos($content, $findme));
echo "Small -> ".$content;
EDIT: btw, make sure to use xwero's example of this string-centric technique above because it has some error trapping. that may be why the benchmarks put it slower than inparo's explode() approach.
EDIT: actually i just went back and tested and you don't need error trapping at all in either approach - both nested functions handle varied text input conditions without crying.