$re = '/^(\-{0,1})(?:(?:0*)(\d+))?((?:\.)(?:\d*?))?0*$/m';
$str = '-0.002506000
1
01
10
1.25
01.250
0
0002345000
0.25
0.50
0.5
0.75000
1000
0001.111
0001.5
.25
01234
-00.1
.2500
.0256
-.010';
$subst = "$1$2$3";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php