如何在字符串中获取带点的数字数据？

Question

There is a string variable containing number data with dots , say $x = "OP/1.1.2/DIR"; . The position of the number data may change at any circumstance by user desire by modifying it inside the application , and the slash bar may be changed by any other character ; but the dotted number data is mandatory. So how to extract the dotted number data , here 1.1.2, from the string ?

Answer 1

Use a regular expression:

(\d+(?:\.\d+)*)

Breakdown:

• \d+ look for one or more digits
• \. a literal decimal . character
• \d+ followed by one or more digits again
• (...)* this means match 0 or more occurrences of this pattern
• (?:...) this tells the engine not to create a backreference for this group (basically, we don't use the reference, so it's pointless to have one)

You haven't given much information about the data, so I've made the following assumptions:

• The data will always contain at least one number
• The data may contain only a number without a dot
• The data may contain multi-digit numbers
• The numbers themselves may contain any number of dot/digit pairs

If any of these assumptions are incorrect, you'll have to modify the regular expression.

Example usage:

$x = "OP/1.1.2/DIR";

if (!preg_match('/(\d+(\.\d+)*)/', $x, $matches)) {
    // Could not find a matching number in the data - handle this appropriately
} else {
    var_dump($matches[1]); // string(5) "1.1.2"
}