可以使用单个正则表达式完成此操作

Question

I have a series of strings in the form:

{ method_name { $key1 = 'quoted value' , $key2 = __('literal value'); }}

// Missing method_name and final semi-colon
// Still valid
{{ $key1 = 'quoted value' , $key2 = __('literal value') }}

// Optional key values
{ method_name { $key1 = , $key2 = __('literal value'); }}
{ method_name { $key1, $key2 = __('literal value'); }}

// Any number of values
{ method_name { $key1 = 'quoted value' , $keyN = 3.14; }}

Currently, I use a series of preg_split and trim. This is part of a custom template engine where method_name informs the parser which method to call and $key = value will be passed to the method as an array. These strings are embedded in a HTML template and that DOM structure may be repeated. Think of it as a table with each row/column having a different value. The keys are the column details (name,sortable etc.) and the method will fill in details of the cell.

The problem I'm having is speed.

Q1. How can I do this with a single expression?

Q2. Will I gain any speed?

Q3. Provided I cache the result, is readability preferred over a somewhat complicated regex?

Q4. Is there any way I can restructure the strings for a performance boost?

Ideally, I'd like to scan the string only once, convert it to PHP code, and do an eval each time it needs to be used.

Answer 1

I would perhaps use a regex like this (I found some parts to simplify from the one in the comments):

(?:\{ (?:(?<method>.+?)\s+\{)?|\G)[,\s]*(?<key>\$\w+)(?: = (?<value>[^,
;}]*))?

The named capture groups are self explanatory, but here's a breakdown:

(?:
    \{ 
    (?:
        (?<method>.+?)   # Captures everything until the next { for the method
        \s+\{       
    )?                   # All this optional
    |
    \G                   # Or \G anchor, which will allow successive match of multiple key/value pairs
)
[,\s]*                   # Any spaces and commas
(?<key>\$\w+)            # Capture of key with format $\w+
(?: = 
    (?<value>[^,
;}]*)  # Capture of value
)?                       # All this optional

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