Código PHP:
$tucontenido= " d fjdklsfjdklsfj dkslfj klsdjf ldsñfj lsdfj kdlsfj dsfj dsñjf klsdfj kdsfh siryhf 89ehfszhdfjksdf jdfdks,f efh dfhkdsfhkndljn dkfjdklsfj dsfj dksfjkdsfj dksjf ohfrdfhdfh dsfh djfhjkfh fh dksfh djkfh djsfh dksjfh safrh eafhdjfhdfhcbfcjfbdhf dfhdhfjdfhdafhsafhudfhaerfewáod jafkdkjf dafhdkzf hpehrajdbzjfdh afhdfhapraDJAKFHADJFHDASFH DAKFH ADSFH ADiu jaifjsdfdsfnesaujr8wryqrhdna hdwerdjfgdafhl";
echo substr ($tucontenido, 0, 100);
...
