10.2. Member Variable Notes
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## 10.2. Member Variable Notes

This section contains details on some of the PHPlot class member variables listed in the previous section. Remember that all PHPlot class member variables are meant for internal use only.

### 10.2.1. datatypes[]

The `datatypes[]` array contains information about the available data types. See Section 3.3, “PHPlot Data Types” for more information about data types. It is used by SetDataType to validated the supplied data type, and by DecodeDataType to set the flags that describe the datatype.

The goal is to keep the names and details about the data types in this array only, and minimize other uses of the actual data type names. However, each plot type drawing function (for example DrawLines) also 'knows' about the data types it supports, and specifies the data type names when calling CheckDataType.

This array was added in PHPlot-6.1.0. It is a protected static member variable in the PHPlot class, so it must be accessed as `self::$datatypes` from inside the class (or a derived class), and not through an instance of the class. Is not accessible from outside the class or derived classes.

The array keys are the data types (for example: 'text-data'). The values are arrays which contain information about the data type. The second-level array keys correspond to the 'datatype' flag variables, without the 'datatype_' prefix. A key will be present, with the value `TRUE`, if the flag should be set for that data type. The key will be absent if the flag should not be set. For example: for data type `text-data`, the array contains one value: `'implied' => TRUE`. This means that for data type text-data, the `datatype_implied` flag should be TRUE (indicating that this data type has implied independent variable values), and all other flags should be FALSE. In addition to `implied`, the other possible keys are `pie_single`, `error_bars`, `swapped_xy`, and `yz`.

### 10.2.2. fonts[]

The `fonts[]` array contains information about the fonts to use for text on the plot. The array keys are the element names (such as `title` or `legend`) as used in SetFont, SetFontGD, or SetFontTTF. The array values are arrays which contain information about the font to use for that element. The keys and values of the second-level arrays are:

Key | Value for TTF | Value for GD Font
--- | --- | ---
ttf | True for a TrueType font | False for a GD font
font | Pathname of the font file | Font number: 1 through 5
size | Font point size | Not used
height | Height in pixels of an upper-case "E" in the font | Font height in pixels
width | Width in pixels of an upper-case "E" in the font | Font width in pixels
spacing | Font's built-in inter-line spacing | Not used
line_spacing | User-requested inter-line spacing factor. | Same as for TTF

For TrueType fonts, the height and width can vary by character. The fonts array stores a height and width value for the font, but these are only used for sizing non-text plot elements (such as the legend color boxes). When PHPlot needs to know the drawn size of a string that will use TTF, it calculates the exact size of that specific string when drawn with the designated font.

GD fonts have fixed character width and height, so the values stored in the fonts array can be used to calculate text string sizes.

The `spacing` key stores the TrueType font's built-in inter-line spacing. Although TrueType fonts have this information internally, PHP cannot access it, so PHPlot calculates it by taking the height of the string "E\nE" and subtracting twice the height of the letter E.

The `line_spacing` key stores the user-specified line spacing adjustment for a text element, if any, from SetFont or one of the two related functions. It will be NULL if the spacing was not set for this element, meaning use the default line spacing. See SetLineSpacing for more information on how this is used.

Here is an example of part of a fonts array, for the title element:

    $plot->fonts['title'] = array(
        'ttf' => FALSE,          // This element uses a GD font
        'font' => 2,             // Use GD font 2
        'height' => 13,          // Provided by GD
        'width' => 6,            // Provided by GD
        'line_spacing' => NULL,  // Use default line spacing
    )

### 10.2.3. label_format[]

The `label_format[]` array contains information about how text labels should be formatted. This array has 5 entries, with keys 'x', 'y', 'xd', 'yd', and 'p'. The 'x' and 'y' entries are for tick labels, and the 'xd' and 'yd' entries are for data labels. (Note that PHPlot defaults data label formatting to match tick label formatting, but this is handled in CheckLabels, with the tick label format information copied to the data label format information if necessary.) The 'p' entry is for pie chart labels, and will only exist for pie charts. (The 'p' entry was added in PHPlot-5.6.0.)

The value of each entry in `label_format` is an array containing formatting information. The arrays are empty by default, meaning there is no special formatting. If formatting has been enabled, for example with SetXLabelType, the arrays can contain the following keys and values:

Key | Used with type | Value
--- | --- | ---
type |  | Formatting type: data, time, printf, or custom.
precision | data | The number of decimal positions to produce.
prefix | data | A prefix string to append to the label (for example, a currency sign).
suffix | data | A suffix string to append to the label (for example, a currency sign or percent sign). This replaces data_units_text (which still works too).
time_format | time | The date/time format string for the PHP strftime() function.
printf_format | printf | The format string for the PHP printf() function.
custom_callback | custom | The function (or array with object and method name) to call to format the label.
custom_arg | custom | An additional argument to pass to the custom_callback function.

### 10.2.4. legend_pos[]

The `legend_pos[]` array contains information about positioning of the legend. This is set by SetLegendPosition, and by the functions which use it (SetLegendPixels and SetLegendWorld). This was added in PHPlot-5.4.0, replacing scalar variables legend_x_pos, legend_y_pos, and legend_xy_world.

The array keys correspond to the arguments to SetLegendPosition and are shown in the following table.

Keys | Value
--- | ---
x, y | Relative coordinates of a point on the legend box
mode | One of: image, plot, title, or world
x_base, y_base | Relative coordinates of a point on the image, plot, or title, or world coordinates
x_offset, y_offset | Pixel offset to be applied last

### 10.2.5. plots[]

The `plots[]` array contains information about known plot types. It is used by FindDataLimits, DrawGraph, and other class functions to prepare for and draw the main portion of the plot. The goal is to contain the information about each available plot type in a single place - this array. The actual names of the plot types (for example 'bars' or 'linepoints') appear only in this array. To simplify somewhat, adding a new plot type to PHPlot involves adding a new element to the `plots[]` array, and adding a new function to PHPlot which draws the 'insides' of the plot.

This array was added in PHPlot-5.3.0. It is a protected static member variable in the PHPlot class, so it must be accessed as `self::$plots` from inside the class (or a derived class), and not through an instance of the class. Is not accessible from outside the class or derived classes.

The array keys are the plot types (for example: 'bars', 'linepoints'). These must not include upper case letters. The values are arrays which contain information about the plot type. The keys and values of the second-level arrays are:

Key | Value
--- | ---
draw_method | Name of the PHPlot class method (function) to call to draw the 'insides' of the plot. This is the only required entry.
draw_arg | Optional argument array to pass to the draw_method function.
suppress_axes | Optional flag indicating that the X axis and Y axis should not be drawn. Default is FALSE.
abs_vals | Optional flag indicating that the plot type uses the absolute values of data. Default is FALSE.
sum_vals | Optional flag indicating that the plot type sums up the values in each row. Default is FALSE.
legend_alt_marker | Optional alternate marker mode for legends: box, shape, or line.
adjust_type | Optional control for adjusting the end of an automatically calculated plot range (see notes below).

Only the `draw_method` entry is required. The named method is used to draw everything inside the plot area. (That is, everything except the plot titles, axis lines, tick marks and tick labels, grid lines, and legend.)

The `draw_arg` entry can be used to pass constant arguments to the `draw_method` method. If present, this must be an array, and each element of the array is passed to the drawing method as a separate argument. If this is not specified, the drawing method is called with no arguments. This is generally used to overload drawing methods, so they handle multiple similar plot types.

The `suppress_axes` flag indicates that X and Y axis lines should not be drawn (used with pie charts, for example). If omitted, FALSE is used, meaning the axis lines are drawn. (Before PHPlot-6.0.0 this was called `draw_axes`, with default TRUE, and FALSE for pie charts.)

The two special data processing flags `abs_vals` and `sum_vals` are used by FindDataLimits to indicate how to compute the minimum and maximum data values. Plot types that ignore sign and take absolute values of the data set `abs_vals` to TRUE. Plot types that sum up the data values in each row set `sum_vals` to TRUE. The default if omitted for both flags is FALSE, meaning the plot type uses the values as specified in the data array. If both `abs_vals` and `sum_vals` are TRUE, this means the plot type sums up the absolute values from the data array. (The stackedarea plot type does this.)

The optional `legend_alt_marker` entry indicates the use of an alternate maker shape in legends. Use SetLegendUseShapes to select either the primary mode or the alternate mode for legend shapes. The primary mode is a solid filled color box. The alternate mode varies with the plot type, according the the `legend_alt_marker` entry. Use 'box' for rectangular color boxes. This is the default if the `legend_alt_marker` key is omitted from the array. Effectively, this means there is no alternate marker mode for these plot types, because color boxes are the primary mode. Use 'shape' for point shape markers, which applies to points plots and similar types which use point shapes. Use 'line' for short line segments, which applies to line plots and similar types.

The optional `adjust_type` entry controls adjustments made to the end of an automatically calculated plot range. See TuneXAutoRange and TuneYAutoRange for more information. This is used to indicate when a plot type needs additional space, perhaps for labels, between the data extrema and the edge of the plot area. If omitted, the default value 0 is used. A value of 0 means apply the adjustment for the dependent variable only. A value of 1 means apply the adjustment for both X and Y, and a value of 2 means do not apply the adjustment to either X or Y.

### 10.2.6. rangectl[]

The `rangectl[]` array contains parameters which are used to control the automatic calculation of the plot area range.

The array contains 2 arrays, indexed as `'x'` and `'y'` for X and Y axis parameters respectively. The keys and values of the second-level arrays are:

Key | Default | Description
--- | --- | ---
zero_magnet | 0.857142 (Note this is 6/7) | Strength of the zero magnet
adjust_mode | T | End adjustment mode: R, T, or I
adjust_amount | (Dynamic; see GetRangeEndAdjust) | Amount of end adjustment, as a fraction of the plot range

Values in this array are set with TuneXAutoRange and TuneYAutoRange. For more information see Section 4.6.4, “Automatic Range Parameters”. The values are used by CalcPlotRange.

### 10.2.7. tickctl[]

The `tickctl[]` array contains parameters which are used to control the automatic calculation of tick intervals.

The array contains 2 arrays, indexed as `'x'` and `'y'` for X and Y axis parameters respectively. The keys and values of the second-level arrays are:

Key | Default | Description
--- | --- | ---
min_ticks | 8 | Minimum number of tick intervals
tick_mode | NULL (calculated) | Tick increment calculation mode: 'decimal', 'binary', or 'date'
tick_inc_integer | FALSE | If TRUE, force the tick increment to be a whole number

Values in this array are set with TuneXAutoTicks and TuneYAutoTicks. For more information see Section 4.6.8, “Automatic Tick Increment Parameters”. The values are used by CalcStep.

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