how to extract data(string) using php using regex?

Question

i have tried to extract

$str = "Instant Oatmeal - Corn Flavour 175g (35g x 5)";
preg_match('/(?P<name>.*) (?P<total_weight>\d+)(?P<total_weight_unit>.*) \((?P<unitWeight>\d+)(?P<unitWeight_unit>.*) x (?P<portion_no>\d+)\)/', $str, $m);

it is correct:

Instant Oatmeal - Corn Flavour 175g (35g x 5)
name : Instant Oatmeal - Corn Flavour
total_weight : 175 g
#portion : 5
unit weight : 35 g

However, if i want to extract

$str = "Cholcolate Sandwich Cookies (Tray) 264.6g (29.4g x 9)";

it is incorrect:

Cholcolate Sandwich Cookies (Tray) 264.6g (29.4g x 9)
name : Cholcolate Sandwich Cookies (Tray)
total_weight : 264 .6g
#portion : 9
unit weight : 29 .4g

How to solve this?

total weight should be: total_weight : 264.6g however, it becomes total_weight : 264 .6g the unit should be "g", but it is now ".6g" — red23jordan
– red23jordan, Commented Oct 9, 2011 at 14:32

ridgerunner · Accepted Answer · 2011-10-09 17:20:08Z

3

Use free-spacing mode for non-trivial regexes!

When dealing with non-trivial regexes like this one, you can dramatically improve readability (and maintainability) by writing them in free-spacing format with lots of comments (and indentation for any nested parentheses). Here is your original regex in free spacing format with comments:

$re_orig = '/# Original regex with added comments.
    (?P<name>.*)               # $name:
    [ ]                        # Space separates name from weight.
    (?P<total_weight>\d+)      # $total_weight:
    (?P<total_weight_unit>.*)  # $total_weight_unit:
    [ ]                        # Space separates totalunits from .
    \(                         # Literal parens enclosing portions data.
    (?P<unitWeight>\d+)        # $unitWeight:
    (?P<unitWeight_unit>.*)    # $unitWeight_unit:
    [ ]x[ ]                    # "space-X-space" separates portions data.
    (?P<portion_no>\d+)        # $portion_no:
    \)                         # Literal parens enclosing portions data.
    /x';

Here is an improved version:

$re_improved = '/# Match Name, total weight, units and portions data.
    ^                       # Anchor to start of string.
    (?P<name>.*?)           # $name:
    [ ]+                    # Space(s) separate name from weight.
    (?P<total_weight>       # $total_weight:
      \d+                   # Required integer portion.
      (?:\.\d*)?            # Optional fractional portion.
    )
    (?P<total_weight_unit>  # $total_weight_unit:
      .+?                   # Units consist of any chars.
    )
    [ ]+                    # Space(s) separate total from portions.
    \(                      # Literal parens enclosing portions data.
    (?P<unitWeight>         # $unitWeight:
      \d+                   # Required integer portion.
      (?:\.\d*)?            # Optional fractional portion.
    )
    (?P<unitWeight_unit>    # $unitWeight_unit:
      .+?                   # Units consist of any chars.
    )
    [ ]+x[ ]+               # "space-X-space" separates portions data.
    (?P<portion_no>         # $portion_no:
      \d+                   # Required integer portion.
      (?:\.\d*)?            # Optional fractional portion.
    )
    \)                      # Literal parens enclosing portions data.
    $                       # Anchor to end of string.
    /xi';

Notes:

The expressions for all the numerical quantities has been improved to allow an optional fractional portion.
Added start and end of string anchors.
Added i ignorecase modifier in case the X in the portions data is uppercase.

I'm not sure how you are applying this regex, but this improved regex should solve your immediate problem.

Edit: 2011-10-09 11:17 MDT Changed expression for units to be more lax to allow for cases pointed out by Ilmari Karonen.

edited Oct 9, 2011 at 17:20

answered Oct 9, 2011 at 16:29

ridgerunner

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5 Comments

Ilmari Karonen Over a year ago

\w+ might not be enough for generic unit parsing, if there are any micrograms (μg), Ohms (Ω), Angstroms (Å), degrees (°) or feet and inches (' / ") involved. But I suppose none of those are very likely to appear in cooking recipes. However, fluid ounces (fl. oz) might be a problem.

ridgerunner Over a year ago

@Ilmari Karonen - very good point. Have updated answer. Thanks!

red23jordan Over a year ago

@ridgerunner -thx very much, can you explain "(?:\.\d*)?" and "/xi" to me? I don't know what they mean..thx

ridgerunner Over a year ago

(?:\.\d*)? means: "Optionally match one literal dot followed by zero or more digits." I recommend spending some time learning the basic syntax. A good place to start is with the tutorials at: regular-expressions.info. But if you really want to "know" regex (in the Neo: "I know kung-fu!" sense), I highly recommend: Mastering Regular Expressions (3rd Edition). This was the most useful book I have ever read.

ridgerunner Over a year ago

Regarding: /xi, the / is the closing regex delimiter and the x and i are modifiers that tell the regex-engine to 1.) use free-spacing mode (x), and 2.) ignore case (i). See: PHP PCRE Pattern Modifiers.

FailedDev · Accepted Answer · 2011-10-09 14:40:38Z

2

Use this :

/(?P<name>.*) (?P<total_weight>\b[0-9]*\.?[0-9]+)(?P<total_weight_unit>.*) \((?P<unitWeight>\b[0-9]*\.?[0-9]+)(?P<unitWeight_unit>.*) x (?P<portion_no>\d+)\)/

Your problem is that you are not taking into account floating point numbers. I corrected this. Note that the portion is still an integer but I guess this is logical :)

answered Oct 9, 2011 at 14:40

FailedDev

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Use free-spacing mode for non-trivial regexes!

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Use free-spacing mode for non-trivial regexes!

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