如何使用标记替换字符串中的数组匹配以突出显示，但从不重叠标记？

Question

If my string is:

Once upon a midnight dreary,
while I pondered, weak and weary,
Over many a quaint and curious volume of forgotten lore,

And I wanted to highlight the following strings (sorted by string length to prefer longer string matches) :

ponder,weary,weak,ary,red,we

I want to end up with:

Once upon a midnight dre<span>ary</span>,
while I <span>ponder</span>ed, <span>weak</span> and <span>weary</span>,
Over many a quaint and curious volume of forgotten lore,

How can I avoid (as a simple str_replace() might lead me)?

Once upon a midnight dre<span>ary</span>,
while I <span>ponde<span>r</span>ed</span>, <span><span>we</span>ak</span> and <span><span>we</span><span>ary</span></span>,
Over many a quaint and curious volume of forgotten lore,

Answer 1

Use word boundaries:

$s = <<< EOF
Once upon a midnight dreary,
while I pondered, weak and weary,
Over many a quaint and curious volume of forgotten lore,
EOF;
echo preg_replace('/(^|\s)(weary|weak|we|ary)\b/i', '$1<span>$2</span>', $s);

OUTPUT:

Once upon a midnight dreary,
while I pondered, <span>weak</span> and <span>weary</span>,
Over many a quaint and curious volume of forgotten lore,